KANSAS CITY – David Wells’ balky back will cost him just one start. At least that’s the plan after the veteran lefty underwent an MRI exam in New York yesterday and received an epidural block to alleviate the discomfort in the left sacroiliac area of his back.

“I wasn’t surprised, because after he received a [cortisone] injection [last Thursday], Dr. [Stuart] Hershon told me if it didn’t work [Wells] would have an MRI and an epidural,” GM Brian Cashman said.

Wells, who is a very big piece of the Yankees’ October plans, was forced to leave Monday night’s 12-9 loss to the Royals after three innings because the pain in the area where the sacrum and hip bone come together became too much to handle. In addition to being examined by Hershon, the Yankees’ team doctor, Wells was seen by spine specialist Paul Kuflick. Wells won’t rejoin the team until Monday night when the Yankees open a three-game series against the Royals at Yankee Stadium.

Watching the 40-year-old Wells gingerly move around the mound Monday gave the indication the problem was more serious than it turned out to be, so yesterday’s news was considered good.

“Obviously, if it was more than one start, you would have to think about the DL,” Joe Torre said of Wells, who is 12-3 with a 3.91 ERA and makes $183,000 for each of his next eight starts.

Sterling Hitchcock, who followed Wells into Monday night’s game, will start Saturday against the Orioles at hitter-friendly Camden Yards. Wells will return to the rotation next Friday against the Orioles at Yankee Stadium. For Hitchcock, who is 1-3, it will be his first start this year after 25 relief appearances.

What Wells’ MRI showed wasn’t information the Yankees were willing to share. However, the problem has nothing to do with the surgery Wells underwent in the middle of the 2001 season when he had discs shaved in his lower back while on the White Sox.

“I will let Boomer talk if he wants to,” Cashman said of the pitcher who has been testy about discussing his back since the problem became public on July 25 when he struggled against the Red Sox in Boston.

When Torre was asked what the problem was called, he didn’t dance around the question.

“My only concern is when he pitches again,” Torre said. “He has been having back problems, and this is good news rather than what it could have been. He has been dealing with this for a long time. Hopefully, he can pitch through it.”

In Hitchcock, Torre has a veteran who was a starter until the last two years when he failed to win the No. 5 spot in the Yankees’ rotation. Coming into the season, 189 of Hitchcock’s 242 appearances were in a starting role. He made two starts last year and didn’t get a decision.

“He had a bad inning the last time out,” Torre said of Hitchcock’s third frame Monday night, when he gave up three runs and ran into control problems. “When he gets ahead he has a couple of weapons he can use: the changeup and the splitter. When a left-hander can throw strikes he can cause people problems.”

Torre isn’t looking for Hitchcock to go deep into the game; however he is expecting five innings.